He had described on Thursday how Pistorius knelt at Ms Steenkamp's side and struggled in vain to help her breathe by holding two fingers in her clenched mouth.

Mr Stipp said he went to Pistorius' home after hearing shots fired on the night Ms Steenkamp was killed and found "a lady lying on her back".

"I also noticed a man kneeling on her side, on the left side. I remember the first thing he said when I got there was 'I shot her, I thought she was an intruder. I shot her,'" Mr Stipp told the court.

He said he did not recognise Pistorius, and described how he tried in vain to resuscitate Ms Steenkamp.

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Gallery: Oscar Pistorius Trial: Key Figures

June Steenkamp, mother of Reeva Steenkamp.

He said Pistorius was "crying all the time" and praying that she would not die.

On top of the premeditated murder allegation, Pistorius faces a charge of illegally possessing ammunition and two further counts related to shooting a gun in public in two separate incidents before the killing.

He denies all the charges against him and maintains he shot Ms Steenkamp after mistaking her for an intruder.

The athlete could face 25 years in jail if he is found guilty by Judge Thokozile Masipa. South Africa does not have trials by jury.

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Gallery: Pistorius: A Sporting Pioneer

Pistorius was born in Johannesburg on November 22, 1986. A congenital condition meant he had no bones in his lower legs.